// SPDX-License-Identifier: GPL-2.0-or-later

/*

 * (C) Copyright 2001

 * Wolfgang Denk, DENX Software Engineering, wd@denx.de.

 */

/**

 * @file

 * @brief Date & Time support

 */

#include <common.h>

#include <command.h>

#include <rtc.h>

#define FEBRUARY    2

#define STARTOFTIME   1970

#define SECDAY      86400L

#define SECYR     (SECDAY * 365)

#define leapyear(year)    ((year) % 4 == 0)

#define days_in_year(a)   (leapyear(a) ? 366 : 365)

#define days_in_month(a)  (month_days[(a) - 1])

static int month_days[12] = {

  31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31

};

/*

 * This only works for the Gregorian calendar - i.e. after 1752 (in the UK)

 */

void GregorianDay(struct rtc_time * tm)

{

  int leapsToDate;

  int lastYear;

  int day;

  int MonthOffset[] = { 0,31,59,90,120,151,181,212,243,273,304,334 };

  lastYear=tm->tm_year-1;

  /*

   * Number of leap corrections to apply up to end of last year

   */

  leapsToDate = lastYear/4 - lastYear/100 + lastYear/400;

  /*

   * This year is a leap year if it is divisible by 4 except when it is

   * divisible by 100 unless it is divisible by 400

   *

   * e.g. 1904 was a leap year, 1900 was not, 1996 is, and 2000 will be

   */

  if((tm->tm_year%4==0) &&

     ((tm->tm_year%100!=0) || (tm->tm_year%400==0)) &&

     (tm->tm_mon>2)) {

    /*

     * We are past Feb. 29 in a leap year

     */

    day=1;

  } else {

    day=0;

  }

  day += lastYear*365 + leapsToDate + MonthOffset[tm->tm_mon-1] + tm->tm_mday;

  tm->tm_wday=day%7;

}

void to_tm(int tim, struct rtc_time * tm)

{

  register int    i;

  register long   hms, day;

  day = tim / SECDAY;

  hms = tim % SECDAY;

  /* Hours, minutes, seconds are easy */

  tm->tm_hour = hms / 3600;

  tm->tm_min = (hms % 3600) / 60;

  tm->tm_sec = (hms % 3600) % 60;

  /* Number of years in days */

  for (i = STARTOFTIME; day >= days_in_year(i); i++) {

    day -= days_in_year(i);

  }

  tm->tm_year = i;

  /* Number of months in days left */

  if (leapyear(tm->tm_year)) {

    days_in_month(FEBRUARY) = 29;

  }

  for (i = 1; day >= days_in_month(i); i++) {

    day -= days_in_month(i);

  }

  days_in_month(FEBRUARY) = 28;

  tm->tm_mon = i;

  /* Days are what is left over (+1) from all that. */

  tm->tm_mday = day + 1;

  /*

   * Determine the day of week

   */

  GregorianDay(tm);

}

EXPORT_SYMBOL(to_tm);

/* Converts Gregorian date to seconds since 1970-01-01 00:00:00.

 * Assumes input in normal date format, i.e. 1980-12-31 23:59:59

 * => year=1980, mon=12, day=31, hour=23, min=59, sec=59.

 *

 * [For the Julian calendar (which was used in Russia before 1917,

 * Britain & colonies before 1752, anywhere else before 1582,

 * and is still in use by some communities) leave out the

 * -year/100+year/400 terms, and add 10.]

 *

 * This algorithm was first published by Gauss (I think).

 *

 * WARNING: this function will overflow on 2106-02-07 06:28:16 on

 * machines were long is 32-bit! (However, as time_t is signed, we

 * will already get problems at other places on 2038-01-19 03:14:08)

 */

unsigned long

mktime (unsigned int year, unsigned int mon,

  unsigned int day, unsigned int hour,

  unsigned int min, unsigned int sec)

{

  if (0 >= (int) (mon -= 2)) { /* 1..12 -> 11,12,1..10 */

    mon += 12;    /* Puts Feb last since it has leap day */

    year -= 1;

  }

  return (((

    (unsigned long) (year/4 - year/100 + year/400 + 367*mon/12 + day) +

      year*365 - 719499

      )*24 + hour /* now have hours */

    )*60 + min /* now have minutes */

  )*60 + sec; /* finally seconds */

}

const char *time_str(struct rtc_time *tm)

{

  const char *weekdays[] = { "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat" };

  const char *months[] = { "Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug",

         "Sep", "Oct", "Nov", "Dec" };

  static char buf[128];

  sprintf(buf, "%s %02d %s %4d %02d:%02d:%02d",

      weekdays[tm->tm_wday],

      tm->tm_mday,

      months[tm->tm_mon],

      tm->tm_year + 1900,

      tm->tm_hour,

      tm->tm_min,

      tm->tm_sec);

  return buf;

}